What are the key learning points about energy forms?
Energy can exist in many forms such as chemical, heat, electrical, sound, light, magnetic, Energy stored in squashed, stretched or twisted materials., The energy an object possesses by being in motion. and The energy an object possesses due to its position above the ground..
The Principle of Conservation of Energy states that energy can be changed from one form to another but the total amount of energy does not change.
Energy is measured in joules (J) and 1 J is approximately the energy needed to lift an apple vertically 1 m.
Energy transfer diagrams show the energy conversions that occur in a range of common devices found in everyday life.
What are the different types of energy?
JONNY NELSON: Energy. There are lots of different types and lots of different ways of storing it.
Chemical energy in a sparkler, elastic potential energy that fires a toy into the air, and many, many more.
NARRATOR: Energy can be transferred. But energy can never ever, under any circumstances, be created or destroyed.
Yeah, never ever.
There are though, lots of different ways to store energy including:
Kinetic energy
Internal energy
Elastic potential energy
Gravitational potential energy
Nuclear energy
Magnetic energy
Let's look at some of these in more detail.
Moving objects have kinetic energy. The more mass and speed they have, the more kinetic energy they have.
All objects have internal energy, including both thermal energy contained in the vibration of its particles and also chemical energy stored in the bonds between particles.
Elastic potential energy is stored when an elastic object changes shape in a reversible way, like a catapult. The stretching or squashing stores energy.
Gravitational potential energy is stored when an object is moved higher than or away from a gravitational field. The amount of energy stored depends on:
The vertical height of the object
The strength of the gravitational field
The mass of the object
Batteries are stores of chemical energy that create current and some objects, like a Van der Graaf generator, are statically charged,while others can be magnetised and store magnetic energy.
As mentioned, although energy cannot be created or destroyed, it can be transferred or converted from one type to another.
For instance, one object can heat another cooler object, transferring heat energy.
Energy can also be transferred mechanically through movement when the motion or position of an object changes, such as one ball hitting another on a pool table.
Mechanical waves such as sound waves or the seismic waves created in an earthquake can also transfer energy mechanically.
Electrical energy can be transferred when an electrical circuit is completed. The internal energy stored in a battery is transferred to moving charged particles in the wire.
Lamps transfer visible light and thermal radiation to the surroundings, and when an object falls to the ground, the gravitational potential energy it possessed is converted to kinetic energy.
Even food transfers energy. It contains chemical energy stored in the bonds between particles, and eating and metabolising food creates an energy conversion in the body.
In a similar way, burning an object like wood causes the internal energy in the wood to be converted into heat, sound, and light given out by the flames.
When it comes to energy, there are three main equations that we need to understand and remember:
Kinetic Energy
Kinetic energy = ½ × mass × velocity²
Because velocity is squared, it has a huge impact on the total kinetic energy.
Gravitational Potential Energy
Gravitational potential energy = mass × gravitational field strength × height
Elastic Potential Energy
Elastic potential energy = ½ × force × extension
or
Elastic potential energy = ½ × spring constant × extension²
JONNY: Energy can't be created or destroyed, but it can be and is stored and transferred.
Forms of energy are just different types of energy such as chemical, heat, electrical, sound, light, magnetic, Energy stored in squashed, stretched or twisted materials., The energy an object possesses by being in motion. and The energy an object possesses due to its position above the ground..
Chemical energy is a type of energy.
Coal is an example of an energy resource of (or store of) chemical energy.
Energy forms
The main forms of energy are:
- chemical
- heat
- electrical
- sound
- light
- magnetic
- strain energy
- kinetic
- gravitational potential
Key points
Energy is measured in Joules (J).
Energy is a scalar quantity (it has no direction).
1J is approximately the energy needed to lift an apple vertically 1 m.
Examples of energy forms
| Energy store | Description | Examples |
|---|---|---|
| Magnetic | The energy stored when repelling poles have been pushed closer together or when attracting poles have been pulled further apart. | Fridge magnets, compasses, maglev trains which use magnetic levitation. |
| Heat energy | The total kinetic and potential energy of the particles in an object, in most cases this is the vibrations - also known as the kinetic energy - of particles. In hotter objects, the particles have more internal energy and vibrate faster. | Human bodies, hot coffees, stoves or hobs. Ice particles vibrate slower, but still have energy. |
| Chemical | The energy stored in chemical bonds, such as those between molecules. | Foods, muscles, electrical cells. |
| Kinetic | The energy of a moving object. | Runners, buses, comets. |
| Electrical or electrostatic | The energy stored when repelling charges have been moved closer together or when attracting charges have been pulled further apart. | Thunderclouds, Van De Graaff generators. |
| Strain energy | The energy stored when an object is stretched or squashed. | Drawn catapults, compressed springs, inflated balloons. |
| Sound | Sound is caused by a vibrating object. The vibrations pass to surrounding particles of matter and then from one particle to another in waves. Sound energy moves through solids, liquids and gases as these all have particles to pass on the vibrations. | Music playing through earbuds, a plucked guitar string, someone talking. |
| Gravitational potential | The energy of an object at height. | Aeroplanes, kites, mugs on a table. |
What are energy transfers?
Different forms of energy can be transferred from one form to another.
Energy transfer diagrams show each form of energy - whether it is stored or not - and the processes taking place as energy is transferred.
The energy transfer diagram below shows the useful energy transfer in a car engine.
You can see that a car engine transfers chemical energy, which is stored in the fuel, into The energy an object possesses by being in motion. in the engine and wheels.
This diagram shows the energy transfer for the useful energy transfer in an electric lamp.
You can see that the electric lamp transfers or converts electrical energy into light energy.
Note that these energy transfer diagrams only show the useful energy transfers.
However, car engines are also noisy and hot, and electric lamps also give out heat energy.
What is the Principle of Conservation of Energy?
Key fact
- Energy can be changed from one form to another but cannot be created or destroyed. The total amount of energy does not change.
This energy transfer diagram below for an electric filament lamp shows that most of the electrical energy is transferred as heat energy rather than light energy.
Note that 100 J of electrical energy is supplied to the lamp.
Of this, 10 J is transferred to the surroundings as useful light energy.
The remainder, 90 J (100 J – 10 J) is transferred to the surroundings as wasted heat energy.
The energy transfer to light energy is the useful transfer.
The rest is ‘wasted’.
It is eventually transferred to the surroundings, making them warmer.
This ‘wasted’ energy eventually becomes so spread out that it becomes very difficult to do anything useful with it.
Question
A bulb in an electrical circuit uses 100J of electrical energy.
According to the principle of conservation of energy, what must the total energy output from the bulb be?
Answer
100J.
Energy cannot be created or destroyed so the total energy output from the bulb must be equal to the energy used by the bulb.
Question
If 20J is converted to light energy how much energy is converted to heat?
Answer
80J.
If the bulb used 100J of energy and 20J converted to light energy then the remainder (100 - 20 = 80) must be converted to heat.
Electric lamps
Ordinary electric lamps contain a thin metal filament that glows when electricity passes through it.
However, most of the electrical energy is transferred as heat energy instead of light energy.
Modern energy-saving lamps and LEDs (light-emitting diodes) work in a different way.
They transfer a greater proportion of electrical energy as light energy.
This is the Sankey diagram for a typical LED lamp:
From the diagram, you can see that much less electrical energy is transferred, or 'wasted', as heat energy from the energy-saving lamp.
As the LED bulbs convert more of the input electrical energy into light, they are more efficient than the filament lamp.
How much do you know about energy forms?
More on Unit 1: Energy
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